build_api: Message protos to get packages relevent to a set of paths.

Given a set of file paths, retrieves a list of packages which are
dependent on those files. The intial use case of this is slim builds
where only packages affected by the changes in the CL will be installed
and tested.

BUG=chromium:1111319
TEST=./generate.sh

Change-Id: If35bf41185dafa7b19a45bcd0dfaec732091e797
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2347449
Commit-Queue: Navil Perez <navil@google.com>
Tested-by: Navil Perez <navil@google.com>
Reviewed-by: Alex Klein <saklein@chromium.org>
2 files changed